laboratoire pierre aigrain
électronique et photonique quantiques
laboratoire pierre aigrain

Séminaire 13 septembre 2010

Subhadeep DATTA, Institut Néel - CNRS - Grenoble
Electrical transport properties of carbon nanotubes filled with magnetic particles

Carbon Nanotubes at low temperature behave as Quantum Dots for which charging processes become quantized, giving rise to Coulomb Blockade depending upon the coupling to the leads. Any small change in the electrostatic environment (tuned by the gate electrode) can induce shift of the stability diagram (so called Coulomb Diamonds) of the device, leading to conductivity variation of the Quantum Dot. A carbon nanotube can therefore be a very accurate electrometer [1]. For example, if a magnetic system is electronically coupled to a nanotube, its electron conduction may be influenced by the spin state of the magnetic system (magneto-Coulomb effect).
I am going to talk about the electrical transport measurements of such hybrid systems where a carbon nanotube is filled with magnetic nanoparticles such as Iron (Fe). We find that low-temperature ( 40mK) current-voltage measurements of such devices can show a hysteretic behaviour in conductance with sharp jumps at certain magnetic fields. We explain the results in terms of the magneto-Coulomb effect where the spin flip of the iron island at non-zero magnetic field causes an effective charge variation in the nanotube due to the Zeeman energy.
Our investigations are a step forward towards the study of the magnetic anisotropy of individual nanoparticles. We believe our findings have important implications for sensitive magnetic detectors to study the magnetization reversal of individual magnetic nanoparticle or molecule, even weakly coupled to a carbon nanotube.

[1Bogani, L. & Wernsdorfer, W. Molecular spintronics using single-molecule magnets. Nat. Mater.7, 179-186 (2008).